The director knew the Bourne Identity star didn't want to make the "Disney version" of Benjamin Mee's best-selling memoir about how he bought a dilapidated zoo in Britain with his family following the death of his wife.

Cameron told The Hollywood Reporter he travelled to Austin, Texas, where Matt was filming the Coen brothers' True Grit and gave him the script, a CD of songs that he'd made and a copy of Local Hero, a 1983 film in which Peter Riegert played an oil-company executive sent to buy a remote village in Scotland.

He said: "My instructions were to not just read the script and make a decision."

Matt revealed: "He said: 'I know what you're going to be afraid of; the bad version of this movie is really a movie you don't want to be in. That's what I'm afraid of too'."

The Departed star went for a run in Central Park and listened to Cameron's playlist which included songs by Neil Young, Bob Dylan, Rolling Stones, Cat Stevens and Pete Townshend.

Matt said: "There were all these songs I know but live versions that he got from sound boards, a song like, I'm Open by Eddie Vedder - he gave me a particularly moving version that I've never heard. I kind of finished that run and went, 'that's a really good feeling'."

He was won over by the music and agreed to star in the film with Scarlett Johansson and Elle Fanning.